In recent years, energy prices have been becoming higher and higher. Therefore, energy saving is a common issue in a wide variety of fields. For example, in the field of automobiles, one of means for improving gas mileage is to reduce the weight of a car body. This is the reduction of weight by substituting a metal having a high specific gravity by a plastic having a low specific gravity. However, in order to realize this, it is necessary to overcome the weak points of a resin such as elastic modulus (stiffness), thermal deformation temperature and heat shrinkage by an excellent reinforcing agent.
To meet the above requirements, needle-like basic magnesium sulfate is becoming a promising material. The needle-like basic magnesium sulfate is a reinforcing agent which is a thin needle-like crystal in appearance and has a width (W) of 0.2 to 1 μm and a length (L) of 10 to 150 μm and whose chemical composition is represented by MgSO4.5Mg(OH)2.3H2O. The needle-like basic magnesium sulfate is excellent in the strengthening of flexural modulus (stiffness) but has problems with impact strength and the smoothness of the surface of a molded article.